Effect of shear strain on the photoelectric properties of PtSe 2 with Se vacancy defects: a first-principles study

Abstract This work employs density functional theory (DFT) calculations to systematically investigate the synergistic regulation of structural stability, electronic properties, charge redistribution, and optical response in monolayer PtSe 2 by selenium vacancy defects and shear strain. The introduction of selenium vacancies transforms PtSe 2 from an indirect bandgap semiconductor to a direct bandgap semiconductor, significantly narrowing the bandgap value by 77.63%. Shear strain in both the XY and YX directions further reduced the bandgap by 89.62% and 88.10%, respectively, in a continuous and anisotropic manner, reflecting a unique directional modulation effect of orbital overlap. Optical property calculations indicate that defects suppress intrinsic light absorption and reflection, whereas shear strain induces opposite spectral shifts: XY-oriented shear strain causes spectral blue-shifting with enhanced reflectance, while YX-oriented shear strain induces more pronounced red-shifting with reduced reflectance. These findings reveal the intrinsic mechanism by which vacancy defects and anisotropic shear strain synergistically regulate the electronic and optical behaviour of PtSe 2 , providing theoretical guidance for the design of strain-programmable optoelectronic devices, broadband photodetectors, and flexible electronic systems.